The present invention relates to improvements in apparatus for testing cigarettes or analogous rodshaped articles which constitute or form part of smokers' products. More particularly, the invention relates to improvements in apparatus for testing those end portions of cigarettes, cigars, cigarillos or filter rod sections which contain fibrous material, especially tobacco. Still more particularly, the invention relates to improvements in apparatus which can be used to determine the mass or quantity of fibrous material in the end portions of cigarettes or the like, for example, in both end portions of a plain cigarette, cigar or cigarillo or in that end portion of a filter cigarette, cigarillo or cigar which is remote from the filter tip.
It is well known to test cigarettes for the purpose of determining the mass of tobacco shreds in their end portions. Such testing is desirable because the smoker is annoyed or inconvenienced if the end portions of a plain cigarette or the tobacco-containing end portions of filter cigarettes contain too little tobacco. Thus, additional tobacco shreds are likely to escape during removal of such cigarettes from their packs, the lighting of an improperly filled end portion of a cigarette is likely to produce a flame, and cigarettes with improperly filled tobacco-containing end portions cannot be manipulated properly during transport from a cigarette making machine to storage, into trays, or directly into a packing machine.
Presently known apparatus which test the firmness of tobacco-containing end portions of cigarettes or the like rely primarily on mechanical scanning. Such apparatus employ pins which are biased against the end faces of rod-like tobacco fillers in cigarettes and the extent to which a pin penetrates into the filler is indicative of the mass of tobacco shreds in the tested end portion of the cigarette. An advantage of pin-shaped scanning devices is that, by properly selecting the dimensions of their tobacco-engaging surfaces, the pins can actually produce a firming or densifying effect by compacting the end portion of a filler if the end portion contains less than a satisfactory quantity of tobacco shreds. On the other hand, mechanical scanning devices are likely to damage or deface the cigarettes, and their inertia is relatively high so that the testing cannot be performed at speeds at which the cigarettes issue from a modern high-speed cigarette making machine.
It was further proposed to determine the mass of tobacco particles in the end portions of cigarettes by resorting to a testing apparatus wherein the cigarettes to be tested are transported sideways in the flutes of a drum-shaped conveyor and the conveyor carries a number of electrodes, one for each flute. The electrodes on the conveyor travel past a stationary electrode whereby the capacitance of the capacitor including the stationary electrode and the immediately adjacent mobile electrode indicates or represents the mass of tobacco in the end portion of the respective cigarette. Such testing apparatus are quite expensive and their maintenance cost is high because each mobile electrode must be connected with a source of high-frequency voltage. Moreover, the characteristics of each capacitor including the stationary electrode and any one of the mobile electrodes must be identical; this necessitates a complex calibrating operation which must be carried out by skilled persons.
It is also known to determine the mass of tobacco in successive increments of a continuous wrapped rod-like tobacco filler by causing the filler to travel lengthwise between two stationary electrodes. Such apparatus cannot be used for determining the mass of tobacco in the end portions of discrete cigarettes because the electrodes permit a continuous rod or a single file of cigarettes to move lengthwise but not sideways.